A controller or inverter provides output signals for controlling an electric machine or motor for a vehicle or other equipment. If the inverter or the electric machine malfunctions or has degraded performance, the output signal of the inverter may become inconsistent with a commanded torque supplied via a vehicle data bus (e.g., a controller area network data bus). In certain prior art, if the malfunction or performance degradation is not detected as a ground fault, short circuit or open circuit; a diagnostic system of the inverter may not identify the malfunction, which can temporarily mask or conceal an impending failure of the inverter or electric machine. An inverter or vehicle drive system that is susceptible to failure at an inopportune juncture might not comply with an applicable reliability standard or industrial safety standard. Thus, there is a need for an inverter and method for controlling an electric motor that supports control or shut-down of the inverter via a vehicle controller or other external controller to foster improved reliability.